Thanks for the info. I live in Tn - zone 6 - I have enough plastic to give it a second layer if needs be. So be it - I will erect it in the garden.
I used a row cover which lets in sun and rain. As the temps got colder, I covered with straw and then with a Styrofoam egg crate mattress during the colder weather.
Once the snow melts and temps improved, I could just roll back the mattress. I also lined the planted area with black milk jugs full of water to give off heat.
Keep me posted on how your project works out.